


To slowly grow together

by Anonymous



Category: Voltron: Legendary Defender
Genre: Alternate Universe - Human, Consensual Underage Sex, Cunnilingus, F/M, Intercrural Sex, M/M, Sex Toys, Sexual Experimentation, Sibling Incest, Trans Keith (Voltron), Voyeurism, afab language, belly bulge, this sounds way kinkier than it is it's actually so soft, using parents toys
Language: English
Status: Completed
Published: 2021-01-31
Updated: 2021-01-31
Packaged: 2021-03-17 23:27:50
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 4,007
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29108565
Author URL: https://archiveofourown.org/
Summary: The boys learn to love themselves and each other.
Relationships: Brief krolitex, Keith/Shiro (Voltron)
Comments: 2
Kudos: 74
Collections: Anonymous





	To slowly grow together

**Author's Note:**

> Keith is referred to as Kee at the very beginning of this when they are young children. If that is going to be triggering, you may want to steer clear of this one.
> 
> Ages are up for interpretation, I never mention specifics, but there's roughly a 3-4 year age gap between them.
> 
> Afab language used.

Takashi tells his parents very matter-of-factly that he is going to marry his baby sister Kee because he loves her and Matt told him at that you're supposed to marry the person you love /the most when they were playing on the jungle gym at school. He was going to marry Adam. But he loves Kee an awful lot more than he loves Adam. Tex and Krolia smile indulgently and tell him he will have to wait until they're both much older to think about that. 

As much as Shiro adores Kee, Kee adores her big brother just as much. She loves when he kisses and snuggles her. She loves that he lets her sleep with him when she has nightmares. She loves that he lets her wear his clothes and be the Prince who saves Princess Shiro when they play together. 

When they get a few years older, Shiro asks Kee if she will marry him. Kee laughs at her silly older brother and they dig her dingy white tutu -- long having turned an off color from being worn on one two many trips to the creek-- out of her closet and Shiro puts it over his face and Shiro's toy lion officiates a ceremony in their garden. Kee lifts up the veil covering Shiro's face and kisses him right on the mouth. Just like Mama and Papa. 

When they get a little older, Kee is curled up in Shiro's narrow twin bed with him on Christmas Eve. They're too old to believe in Santa, but they're still too excited to sleep. Shiro asks Kee if she will still marry him even though he's sick now. Kee asks him if he will still marry her if she wants him to call her "Keith."

A few years later, Shiro is down one disease and one arm, but his baby brother loves him all the same. Keith fights viciously when anyone tries to say Shiro can't or shouldn't do something and Shiro fights for Keith in return when people say he's confused and troubled. 

Their Mama and Papa are so proud of them. They assume their boys will eventually grow out of this phase where they slip into each other's rooms at night. But they won't press because their boys are so close and so protective of each other. Like family ought to be. They love seeing their boys being affectionate with and doting on each other and hope maybe they're doing a little bit of good in helping to raise a sensitive and emotionally intelligent pair of young men. But at night when their parents aren't around and they're hidden under blankets in the dark, Shiro and Keith press shy kisses to each other's mouths and hold each other so close. It's tender, intimate affection at its purest. 

And then Shiro happens to see their Papa Treating Their Mama Right one afternoon. He'd come inside to get drinks for himself and Keith and Papa had Mama laid out on the kitchen counter. He massaged one of her breasts while he sucked at the other one. Shiro watched Papa slip down and tug Mamas strong thighs over his shoulders so he could bury his face between her legs.

Shiro runs from the house back to where he and Keith had been working on homework in the yard. He says they should take a break and go get food in town. If the way Keith easily presses his lithe body against Shiro's back on the hoverbike makes his stomach swoop more than how he was taking his turns.... Well. He wasn't going to think too hard about it.

A few nights later, when Keith was snuggled against his chest after having had a rough day at school, Shiro made up his mind. He had kissed the tears off Keith's ruddy cheeks and tucked him close. Keith was angry though. At the asshole kids at school and at his body. Maybe it was self-important for Shiro to think he could be the person to make Keith feel better, but he couldn't stand to see Keith this way. 

He told Keith he was going to kiss him before he did, and when he gently pushed his tongue into the younger's mouth he was met with unbridled, clumsy enthusiasm.

Keith's eyes were dancing when Shiro pulled back, one hand was petting gently over Keith's side and the other cupped his face. Shiro was kneeling overtop of his little brother and giving him a shy smile, knees on either side of his gently flared hips. 

"That was good?" Keith asked, tonguing at his kiss-plush lips.

"I think so." Shiro couldn't stop smiling. So he leaned down and kissed Keith again, trying for something softer, but Keith surged up and their teeth clacked and there was too much spit. They parted giggling against each other's mouths. 

"I love you, Shiro." 

And even though he had heard it a million times before, this was different. 

"I love you too, Keith."

Things evolved as they got older and gained more knowledge. Shiro still desperately wanted to make Keith shout in pleasure the way Papa Tex had made their Mama do that day he'd accidentally peeped on them.

They continued to trade soft kisses whenever they could. Which was mostly in the dead of night in one of their beds. Occasionally Keith would crawl into his big brothers lap on the couch though and press flirty giggling kisses to his mouth and jaw after they finished homework. Or Shiro would situate himself between Keith's thighs where he was perched on the counter as they shared a pint of ice cream after they parents went to bed and lick the remnants of Cherry Garcia from his pretty pink lips.

Things were good. Better now that he and Keith were going to the Garrison together and he and his friends could support Keith with his bully problem throughout the day. 

The first time Keith pressed his hands to his unbound chest with intention while the shared their nighttime kisses, things felt even better. He took a moment to react as his brain shorted out, but when Keith made a curious sound around Shiro's tongue in his mouth, he moved gently. It wasn't as though he hadn't felt the impossibly soft flesh there before, but not with his open palm, and ample time and permission. This was nothing like hugging Keith to his chest and enjoying the gentle smush of their bodies together. 

Keith made the softest noises when he cupped one and then the other through his thin nightshirt. He qtook his hands away to press them to the skin of Keith's stomach, freed by his shirt riding up during their cuddling. His hand moved up, slowly, offering Keith an out should he want it. Keith's skin was impossibly soft when he smoothed his palm over the small swell of his chest. Keith gasped and Shiro felt his nipple peak under his hand. 

Shiro had to ask. "Is this okay, Keith?"

Keith's eyes were so open.

"Everything is okay, as long as it's you, Shiro."

Shiro lowered his head to rest against Keith's breastbone, his hand trailed back down his brother's side and squeezed his hip. 

Keith let his eyes slip closed and brought his hands up to card through his brother's hair. "I mean it…"

"I know. Thank you for trusting me…" Shiro turned his head to kiss the soft fabric he had been resting his head on and Keith shifted under him in anticipation. His shirt was eased up and when Shiro kissed his skin he shivered. 

Shiro eased up and pressed an easy kiss to Keith's plush bottom lip before coming back to kiss at his chest. First one small breast and then the other was kissed and licked and sucked at. Keith's pale skin bloomed red and violet under Shiro's mouth and his fingers tugged at his hair while he made quiet noises of want. 

Shiro lowered himself even more to nose at Keith's belly button, enjoying the cute bubble of laughter and way his stomach rolled to get away from the tickle. He kissed at Keith's hipbones through his boxers and then looked up for permission. Keith's cheeks were pink and he was worrying his bottom lip. Shiro stroked his thumb under the hem of the fabric across his brother's smooth thigh. 

"You are so beautiful…" 

Keith blushed. "What are you gonna do?"

Shiro blushed at the question. He wanted to do a lot of things with Keith, but his practical knowledge was limited. And he didn't want it to be like the guys in the locker room making salivious comments about what they wanted to do to Professor Allura Altea or once he had even overheard someone say something about their own mother, Lieutenant Krolia Kogane. He wanted what he had seen that day in the kitchen, what he had heard many times over the years late at night through the wall, what they had been teasing at for months.

"Let me make you feel good?"

Keith's blush got impossibly darker, but as he whimpered and his thighs flexed sharply. The fabric was wet within moments and it was pulsing under his tongue. He pulled away to help Keith get his boxers off after Keith's legs began trembling, but lowered himself once again to lick at the little nub he had found. 

Without the fabric in the way he could see the wetness starting to sleep onto the plush lips on Keith's pussy too, making the lower half of the seam shiny with slick. 

He licked over it and felt a bubble of pride swell in his chest. /He was making Keith feel this good. 

Keith's hips bucked and he gasped sharply as he teased the tip of his tongue under the hood of his clit. 

"T-takashi!"

Shiro kneaded at his thighs and let his brother ride against his tongue. The sounds he was starting to make were so good. So pretty. 

Shiro latched his lips around it and continued the steady rhythm of his tongue. And then he sucked.

Keith bowed beautifully, thighs clenching on either side of his brother's head as he came. 

Shiro finally pulled back when Keith let out a whimper and gave his baby brother a smile. He ran his thumb down the slick seam of his pussy and gently parted the wet folds. Keith made a small noise of protest, but Shiro shushed him and leaned back in to clean him of his mess in gentle broad strokes of his tongue. He pressed the flat to the tiny hole he had exposed and rubbed across it, coaxing more slick from him. When he was satisfied that Keith was clean, he sat back on his haunches and grinned again.

Keith was panting and Shiro's dick was jumping with interest as he enjoyed the way his brother's blush painted over his face and down his chest. 

Shiro moved forward to kneel over Keith again and slipped his thumb into the apex of his brother's folds and rubbed over his clit slowly. 

"Still okay?" 

Keith turned dazed eyes to him and nodded. "Better than okay…"

"Want to keep going?"

Keith squirmed a little as he nodded. Shiro leaned down to kiss at the sensitive skin of his brother's hips and kept his thumb slow and firm on his clit.

"I wanna make you feel good too."

Shiro startled a little and looked up to meet bashful violet eyes, hand pausing. He didn't even know how to respond to that.

Keith worried his lip and pushed himself to sit up. "You don't have to...put it /in if you don't want to. I could just…" He made an incredibly vague hand motion.

"Do you want me to put it in?" He asked, a little breathless.

Keith shrugged. "Eventually…"

Shiro rose to kiss the tip of Keith's nose. "Until it's a 'Damn it, Takashi, right now!' it's a 'No.'" He gave a crooked boyish grin and pressed a finger to Keith's lips as he started to protest. "And that's okay. I would wait forever for you, Keith… I hope you know that. And even if it's never, there are still other things we can do."

That brought a smile to Keith's face.

"Like what?" Keith's tone was just this side of too innocent.

"Brat." 

Keith stuck his tongue out and flopped back onto the bed.

Shiro settled next to him again and brushed his bangs out of his eyes. Keith wiggled closer and angled his hip into Shiro's to rub against the hardness that had been straining his sweat pants for much longer than he cared to admit.

"Roll over? I have an idea…" Shiro gasped out as his hips bucked against his will and his brother's hip.

Keith kissed his chin and turned, letting Shiro guide him up and back with the hand on his hip. Shiro shoved at the waistband of his sweatpants and, after urging Keith to lift his leg a bit, slid his length between his baby brother's folds that were still slick with his own spit. 

Shiro groaned into the nape of Keith's neck and let him relax his leg again, making his pussy hug tighter around his cock. 

"Fuck…." He kissed at Keith's neck. "This okay?"

Keith reached down and slipped his fingertips delicately over the crown of Shiro's cock where it protruded beneath his clit. Shiro shuddered behind him and gave a tentative rock to see how Keith would react to the sensation. 

Shiro could feel his hole contract where the length of his cock slipped against it and cursed again.

Keith whimpered at the slide, the feeling of his pussy trying to drag Shiro's foreskin back up and then the ridge of his mushroomed head catching on his hole before it slid back through and appeared between his legs again. 

"Feels nice," Keith huffed as he joined the easy rhythm Shiro set by rocking his hips back.

"Let me make it feel better…" Shiro hummed and slipped his hand from Keith's hip down to roll his clit with sure fingers above his cock head. He was already leaking precum into Keith's folds and knew he wouldn't last too much longer, but he desperately wanted to make Keith come again too. 

Keith reached back to grab as his hip for leverage as he rolled his hips. Shiro could tell he was biting his lips to try to keep himself quiet from the muffled noises he was making. 

"You feel so good, Keith." Shiro huffed against his ear and dipped his fingers down to catch some of his precum to smear over his brother's clit. "Does that feel good, baby?" 

Keith nodded. "So good, Takashi."

"Are you gonna come again for me? Do you think you can do that?"

Keith's hips jerked, but he nodded.

His hole was drooling slick along the length of Shiro's cock now and his clit was pulsing as he let Shiro take control 

"I'm close, baby. Where do you want me to come?" Shiro kissed at his shoulder.

Keith came as he went to answer, Shiro's cock having caught against his hole just as Shiro picked up the pace of his fingers. Feeling the flex of his brother's hole against the head of his cock took the choice from him as he came against it, slit pressed just inside the scant space. 

Keith snuggled back against him sleepily, panting.

Shiro kissed at his shoulder and carefully pulled his dick from between Keith's legs, cautious of making a bigger mess. "Sorry."

Keith huffed a laugh and twined his hand with Shiro's. He pulled the arm tight around his waist and let go to slip his hand between his legs. Shiro watched, confused, as he brought two fingers coating in Shiro's cum up to inspect them.

He choked on his own tongue when Keith licked the pad of his finger curiously, and then popped them both into his mouth. "Shit."

Keith glanced at him over his shoulder and released his fingers. "Do you want to try?"

"You're going to /kill /me." Shiro face-planted into the pillow and groaned.

Keith laughed and rolled over, tucking himself against his big brother without a care for the mess seeping down his thigh. 

"We can do that again, right?"

"If you want to…"

Keith hummed. "I love you."

"I love you too, Keith."

Keith was voracious after that night. It became increasingly rare that he didn't find his way into Shiro's room at night. His lips were always a soft red from sneaking kisses in stolen moments. He loved to pinch Shiro's nipples or grope his crotch when they passed each other in a deserted area of campus or the halls at home. 

Shiro, being the teen boy he was, wasn't much better. As Keith became more confident in his sexuality, so did Shiro. He found Keith loved to be praised, to be bossed around a little, to be cornered after a day of teasing his big brother and kissed until his boxers were soaked. And he loved being able to give that to him. 

Within a few weeks they were well-versed in getting each other off with their hands, and in a few more their mouths as well. They'd once repeated their venture into non-penetrative sex in the hallway outside their parent's bedroom after they had heard Mama laugh low and then Papa moan. 

Through the crack in the door they watched Mama fuck into Papa's ass with a purple vibrator. Mama smacked his bottom and then did something that made the buzzing louder and Papa cuss. Shiro had pushed Keith against the wall and rucked his shirt up over his tits as Keith shoved down his boxers. Keith had already been wet after making out in the darkened hallway before they'd gotten curious, and Shiro's dripping cock pushed between Keith's lips to fuck against his clit and through his folds with little resistance. Keith had bitten his lip and hung on as his big brother fucked into his folds. He came between them, messily, at the same time Papa shot his load onto Mama's waiting tongue. Shiro had pulled Keith's boxers up and drug him back to his room to finish Keith off and then lick him clean. 

Keith had stolen their parents box of toys while they went on an anniversary trip not long after. Shiro marveled at the collection of brightly colored dicks and looked at Keith questioningly. 

The day had ended with them sword fighting with dildos while standing on the armchair and coffee table respectively, but the next started with a very naked Keith sitting criss cross applesauce on the bed next to him with a bottle of lube and one of the smallest toys the box had to offer. 

Shiro swallowed, already hard from waking up, and watched as his baby brother slicked the vibrator and pressed the blunt tip against his little hole. Keith made a face of discomfort, glanced at Shiro, and then started rubbing a finger over his clit. He pressed again and after a twitch of his hips it was in. He slid the rest in, slow but without pausing and eased it in and out a few times curiously. 

He hummed and looked at Shiro, eyes flicking down to his tented pants. 

"Good morning."

Shiro licked his lips and moved to kneel before his brother as he fucked the toy in and out of his cunt lazily. 

"Hi…" He finally responded. He reached up and cupped Keith's cheek, carefully leaning forward to kiss him. The sweetness of it was highlighted by the slick sounds of the lube and toy. 

"Shiro, I think I'm ready…"

Shiro nodded and reached down to still Keith's hand with the toy pushed as far in as the base would allow. Keith took his hand back and laid all the way down from his former recline. Shiro pumped the toy in and out again, slowly, watching how Keith's hole flexed and jumped at the movement. He leaned down and licked at his clit, teasing, and did it again. In, out, in, out. He sucked and flicked his tongue over the nub and enjoyed Keith's hands in his hair and the soft noises he was making for a few moments before he pulled back and removed the toy completely. 

Keith whined, but Shiro pressed a fingertip to him, gathering slick and lube that he smeared over the head of his cock after he shoved his sweatpants down enough to free it.

"You're sure? I can just use the toy if you want… or--"

"I want you, Shiro…"

"I want you too." He gave him a smile and sat back, gesturing Keith closer. 

Keith clambered into his lap and steadied himself with his hands on Shiro's shoulders. Shiro teased the head of his cock through Keith's folds and against his hole. Keith shivered and slowly began to ease himself onto the length. It was considerably thicker than the toy, but it was warm and yielding, and attached to the young man he loved with everything he was, and he took it with some difficulty and a look of bliss on his face.

Shiro wrapped his fingers tightly at the base of his dick, meanwhile. He was already near shooting off just from going in, his balls were tight and his cock throbbing at the staved off orgasm. When Keith's ass finally met his hips and hand he opened his eyes and marvelled.

Keith was perfect and he was his. Keith wiggled experimentally and gave Shiro a smile. 

"You're inside me."

Shiro had to laugh. "I am…"

Together they figured out a slow rhythm where Shiro pressed his hips up as Keith rolled his forward. The movement pressed the head of Shiro's cock tight to the back of Keith's cunt and made him whine in pleasure. 

"I feel so full," Keith huffed and purposely flexed around him. 

"You feel so tight," Shiro pressed his hand to Keith's belly fondly.

Keith pitched back on a particularly sharp thrust and Shiro gasped as he felt his dick slam against his palm. 

He pushed back gently, holding Keith in place, and rubbed over it, marveling. "Fuck… look how tiny you are…" 

Keith rocked shallowly as his brother teased his body. "'m not tiny, 're just big." He bounced and the end of his protest turned into more of a gurgle as his walls were stroked. 

Shiro shivered and his dick throbbed inside his brother. "Keith, baby, I'm not gonna much longer…" He took Keith's hand and brought it down to where they were joined. "Touch yourself?" 

Keith whined, but started rubbing at his clit. He let Shiro guide his hips in an easy roll, thrusting up as Keith came down and bottoming out each time. 

Keith came quickly, overwhelmed by the fullness inside him and the words of encouragement Shiro had started to whisper to him as he took him.

Shiro drew him down to his chest as he shook through his orgasm, letting him catch his breath. Shiro still pulsed hard and hot inside him, and Keith whined and pressed a kiss to Shiro's jaw. "Come for me?"

His brother whimpered in response and gave a few short, stuttering rocks of his hips before Keith felt him release. He let out a quiet "oh" of wonder at the sensation and smiled against his brother's skin.

Shiro panted, arms still tight around Keith. "Oh?"

"I can feel it… Inside."

Shiro blushed. "Uh…"

"I like it." Keith gave a bashful smile. "Like being yours in this way too…."

It was Shiro's turn to give a quiet "oh."

Keith leaned up enough to press a soft kiss to Shiro's bottom lip and wrinkled his nose at the sensation of his brother's softening length slipping from his body. 

Shiro rolled to his side, tucking Keith in tight to his body as he dragged the blankets back over them. "You are so perfect." 

Keith laughed and snuggled closer. "Nah, just yours."


End file.
